1. Field of the Invention
The present invention relates to compressors for compressing a working fluid such as refrigerant to a required pressure, and more particularly, to an inside frame of a compressor inside of a shell of the compressor for mounting various components of the compressor thereon.
2. Background of the Related Art
The compressor compresses the working fluid, such as gas or a refrigerant, to a required pressure. In the compressors, there are turbo compressors, such as axial compressors, and centrifugal compressors, and displacement compressors, such as rotating compressors, and reciprocating compressors.
Of the compressors, the reciprocating compressor has a piston in a cylinder for reciprocating therein to draw gas or refrigerant into the cylinder, and compress, and discharge the gas or refrigerant.
FIG. 1 illustrates a section of a related art reciprocating compressor.
Referring to FIG. 1, the related art reciprocating compressor (hereafter called as a compressor) is provided with a shell 1 having an upper case 1a and a lower case 1b, for holding various components, and a frame 2 supported on springs 2S inside of the shell 1 for mounting various components of the compressor thereto.
There is a boss having a vertical pass through hole in a central part of the frame 2, with a crankshaft 5 rotatably mounted therein.
The crankshaft 5 has an oil passage 5a, for guiding oil L held in a bottom part of the shell 1 to an upper part of the shell, and spraying the oil onto the frame 2. There is a pumping mechanism 5d at a lower end of the crankshaft 5 for pumping the oil ‘L’ to the oil passage 5a. 
The crankshaft 5 rotates by a motor part having a stator 3 and a rotor 4 fixed to the crankshaft 5 for rotating by an electrical interaction with the stator 3, under the frame.
There is a crank pin 5b on top of the crankshaft 5 eccentric from a rotation center of the crankshaft 5. There is a balance weight 5c opposite to the crank pin 5b, for making a rotation speed of the crankshaft 5 uniform.
In the meantime, there is a cylinder 6 formed as one unit with the frame 2 at one side of an upper part of the shell, with a compression chamber formed therein. There is a piston 7 in the cylinder for compression of refrigerant or gas, connected to the crank pin 5b at top of the crankshaft 5 with a connecting rod 8.
There is a valve assembly 9 on the cylinder 6 for controlling flow of refrigerant into/out of the compression chamber. The valve assembly 9 is provided with a suction valve for drawing refrigerant, and a discharge valve for discharging compressed refrigerant.
The valve assembly 9 is mounted between the cylinder 6 and the head cover 10, and there is a suction silencer 11 at one side of the head cover, connected to the valve assembly, for attenuating noise from the refrigerant.
The shell has one side having a suction pipe 12 fitted thereto for guiding the refrigerant from an outside of the compressor to the suction silencer 11, and the other side having a discharge pipe 13 for discharging compressed refrigerant.
Though the frame 2 is cast together with the boss 2a, the cylinder 6, and the like, the frame 2 may be fabricated separate from the boss 2a or the cylinder 6 and mounted on the frame depending on design conditions.
A structure of a related art frame for mounting the various components of the compressor will be described with reference to FIG. 2, wherein the boss, and the cylinder are fabricated separate from the frame.
Referring to FIG. 2, the frame is pressed or forged. The frame 20 is provided with an upper plate 21 having a boss hole in a central part for inserting a boss 24 therein, legs 22 bent downward, and extended from opposite ends of the upper plate 21, and stator fastening parts 23 bent outward, and extended perpendicular from lower ends of the legs 22 parallel to the upper plate 21.
Each of the stator fastening parts 23 has fastening holes 23a for fastening the stator 3 thereto which is mounted on an underside of the stator fastening parts 23 with fastening means 3a. 
However, the related art frame has the following problems.
First, the stator fastening parts 23 of the frame 20 formed by outward bending, and extension from the legs 16 results in a long total length ‘L’ of the frame 20, that impedes fabrication of a smaller compressor.
Second, the contact of an entire bottom surface of the flange 24a formed at a top of the boss 24 with an edge of the boss hole is liable to cause the boss and the upper plate 21 to misalign so as to be out of a right angle, that impedes smooth rotation of the crankshaft inserted in the boss 24.
Third, the low rigidity of the bent parts 22a and 22b of the frame is liable to cause breakage, or deformation due to stress concentration.
Fourth, in a case of deformation of the frame, relative positions of components mounted on the frame change, to make a performance of the compressor poor.